The semiconductor industry has achieved rapid improvements in integration density of electronic components, which are arisen from continuous reductions in the component size. Ultimately, more of the smaller components are afforded to be integrated into a given area. These improvements are mostly due to the development of new precision and high resolution processing techniques.
During the manufacturing of high resolution integrated circuits (ICs), various processing liquids will come into contact with a bare wafer or a film-coated wafer. For example, the fabrication of a fine metal interconnection typically involves a procedure of coating a base material with a pre-wetting liquid before the base material is coated with a composite liquid to form a resist film. These processing liquids, containing proprietary ingredients and various additives, are known to be a source of contamination of IC wafer.
One can speculate that even if a trace amount of contaminants is mixed into these chemical liquids, such as a wafer pre-wetting liquid or a developer solution, the resulting circuit patterns may have defects. It is known that the presence of very low levels of metal impurities, as low as 1.0 ppt, interferes with the performance and stability of semiconductor devices. And depending on the kind of metallic contaminants, oxide property can deteriorate, inaccurate patterns can be formed, electrical performance of semiconductor circuits can be impaired, which eventually adversely impact manufacturing yields.
The contamination of impurities, such as metal impurities, fine particles, organic impurities, moisture, and the like, can be inadvertently introduced in a chemical liquid during various stages of the manufacturing of the chemical liquid. Examples include a case where impurities are presented in a raw material, or a by-product generated or an unreacted reactant remained when the chemical liquid is manufactured, or foreign matters eluded or extracted from the surface of the manufacturing apparatus or from a container equipment, reaction vessels, or the like used in transporting, storing or reacting. Hence, a reduction or removal of insoluble and soluble contaminants from these chemical liquids used for the production of highly precise and ultra-fine semiconductor electronic circuits is a basic assurance of producing defective-free ICs.
In this respect, it is imperative to significantly improve and to rigorously control the standard and quality of chemical liquid manufacturing processes and systems in order to form high purity chemical liquids, which are indispensable in the fabrication of ultra-fine and immensely precise semiconductor electronic circuits.